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Module Communications Network: Other Ford Focus II

Communication Devices 2 illustrations ~922 words

Powertrain Control Module (PCM)

The PCM is on the controller area network (CAN). The PCM controls the engine for better fuel economy, emissions control, and failure mode detection and storage. For additional information, refer to the INTRODUCTION - GASOLINE .

Restraint Control Module (RCM)

The RCM controls the deployment of the air bags based on sensor input. The RCM is on the CAN. The RCM communicates with the occupant classification sensor using the CAN. The occupant classification sensor does not communicate with the diagnostic tool, and is mentioned here as a possible concern should CAN communication be lost. For additional information, refer to SUPPLEMENTAL RESTRAINT SYSTEM .

Anti-Lock Brake System (ABS) Module

The ABS module and the ABS module with stability assist are connected to the CAN. The ABS module controls the brake pressure to the 4 wheels to keep the vehicle under control while braking. For additional information, refer to VEHICLE DYNAMIC SYSTEMS .

Instrument Cluster

The instrument cluster is connected to the CAN. The instrument cluster displays driver information, including tachometer reading, fuel level, engine coolant level and speed. For additional information, refer to INSTRUMENT CLUSTER .

Occupant Classification Sensor

The occupant classification sensor is connected to the CAN. The occupant classification sensor is located in the passenger seat and is used to determine whether or not to deploy an airbag based on the weight detected in the passenger seat. The occupant classification sensor communicates on the CAN to the RCM only. Diagnosis is carried out through the RCM.

Generic Electronic Module (GEM)

The GEM is on the international standards organization (ISO) 9141 communications network. The GEM controls a variety of systems

  1. windshield wipers
  2. warning chimes
  3. interior lamps
  4. exterior lamps
  5. power windows
  6. security

For additional GEM information, refer to MULTIFUNCTION ELECTRONIC MODULES .

Refer to COMPUTER DATA LINES for schematic and connector information.

SPECIAL TOOL(S) 73III Automotive Meter 105-R0057 or equivalent Worldwide Diagnostic System (WDS) Vehicle Communication Module (VCM) with appropriate adapters, or equivalent diagnostic tool Flex Probe Kit 105-R025B or equivalent

Controller Area Network (CAN)

The CAN is not designed to operate under single point fault conditions. If either circuit is shorted to voltage or CAN data plus is shorted to ground, module-to-module and module-to-tester communication is not possible. If CAN data minus is shorted to ground or an open exists on either bus line, module-to-module and module-to-tester communication is marginal at best. The CAN bus may remain operational when one of the two termination resistors are not present.

International Standards Organization (ISO) 9141 Communications Network

The ISO 9141 communications network does not permit inter-module communication. When the diagnostic tool communicates with the generic electronic module (GEM) on the ISO 9141 communication network, the diagnostic tool must request all information or initiate module commands.

The ISO 9141 communications network does not function if the wire is shorted to ground or battery voltage. Also, if the GEM loses power or shorts internally, ISO 9141 communications will fail.

The GEM is the only module on the ISO 9141 communications network.

Possible Causes

  1. CAN circuit 4-EC7E (GY/RD) open
  2. CAN circuit 4-EC9A (GY) open
  3. CAN circuit 5-EC7E (BU/RD) open
  4. CAN circuit 5-EC9A (BU) open
  5. ABS module C135 (with stability assist)
  6. ABS module C155 (ABS only)
  7. ABS module
  8. DLC C251
  1. CAN circuit 4-EC7 (GY/RD) open
  2. CAN circuit 5-EC7 (BU/RD) open
  3. PCM C175b
  4. PCM
  5. DLC C251
  1. CAN circuit 4-EC7B (GY/RD) open
  2. CAN circuit 5-EC7B (BU/RD) open
  3. instrument cluster C2220
  4. instrument cluster
  5. DLC C251
  1. CAN circuit 4-EC7E (GY/RD) open
  2. CAN circuit 4-EC18 (GY/BK) open
  3. CAN circuit 5-EC7E (BU/RD) open
  4. CAN circuit 5-EC18 (BU/BK) open
  5. DLC C251
  6. RCM C2041b
  7. RCM
  1. ISO 9141 communications network circuit 8-EE9 (WH/GN) open, short to ground or voltage
  2. DLC C251
  3. GEM C201d
  4. GEM
  1. CAN circuit 4-EC7E (GY/RD) open, short to ground or voltage
  2. CAN circuit 5-EC7E (BU/RD) open, short to ground or voltage
  3. DLC C251
  4. ABS module C135
  5. instrument cluster C2220
  6. PCM C175b
  7. RCM C2041b
  8. occupant classification sensor C3043
  9. ABS module
  10. instrument cluster
  11. PCM
  12. RCM
  13. occupant classification sensor
  1. fuse
  2. DLC C251
  3. diagnostic tool
  4. circuit 29-RA1 (OG) open
  5. circuit 31-RA1 (BK) open
  6. circuit 91-RA1 (BK/OG) open

Scheme 14

Scheme 14: PINPOINT TEST G: NO MODULE/NETWORK COMMUNICATION - NO POWER TO THE DIAGNOSTIC TOOL
Scheme 14: PINPOINT TEST G: NO MODULE/NETWORK COMMUNICATION - NO POWER TO THE DIAGNOSTIC TOOL

Scheme 15

Scheme 15
Scheme 15
  1. G1 CHECK THE DIAGNOSTIC TOOL CONNECTOR Inspect the diagnostic tool pins for damage. Are the pins OK? Yes : GO to G2 . No : REPAIR the diagnostic tool connector. CLEAR the DTCs. REPEAT the self-test. CARRY OUT the data link diagnostics test.
  2. G2 CHECK THE DLC C251 FOR DAMAGE Key in OFF position. Inspect the DLC C251 pins for damage. Are the pins OK? Yes : GO to G3 . No : REPAIR the DLC C251. CLEAR the DTCs. REPEAT the self-test. CARRY OUT the data link diagnostics test.
  3. G3 CHECK THE VOLTAGE TO THE DIAGNOSTIC TOOL Key in ON position. Measure the voltage between the DLC C251-16, circuit 29-RA1 (OG), harness side and ground. Is the voltage greater than 10 volts? Yes : GO to G4 . No : VERIFY the CJB fuse 48 (10A) is OK. If OK, REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test. CARRY OUT the data link diagnostics test.
  4. G4 CHECK THE DLC GROUND CIRCUITS Key in OFF position. Measure the resistance between the DLC C251-44, circuit 31-RA1 (BK), harness side and ground; and between the DLC C251-5, circuit 91-RA1 (BK/OG), harness side and ground. Are the resistances less than 5 ohms? Yes : REPAIR the diagnostic tool. CLEAR the DTCs. REPEAT the self-test. CARRY OUT the data link diagnostics test. No : REPAIR the circuit in question. CLEAR the DTCs. REPEAT the self-test. CARRY OUT the data link diagnostics test.

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